Light weight clay product and process of making



Patented Apr. 9, 1935 LIGHT WEIGHT CLAY PRODUCT AND Y PROCESS 10F MAKING Charles Weigel, Hebron, N. Dak.-

No Drawing. Application October 22, 1930,

,. Serial .No. 490,536

10 Claims. (Cl.,106-21) The invention relates to structural ceramic material and to the process of manufacturing. the

same, the principal object of the invention being to produce such material preferably in brickor block form, which, while possessing great strength and resistance to stress, is of very light weight, and has a high insulating value.

The present application is a continuation in part of my prior application Serial No. 151,028,

filed Nov 26, 1926, for Brick and process of manufacturing same. I p

A further object of the invention is to produce a block which is cellular in structure and which is sound proof and possessed of fine acoustical properties. l

A still further object is to produce a ceramic block into which nails or other fastening means may be driven without cracking or splitting the block.

Still another object is to produce a cellular block in whichthe size of, the cells may be regulated as desired, during the course of manufac ture ofthe block.

A still further object is to provide a block or brick having a very porous face which is especially adapted to receive and retain a plaster or like coating. 1

Another and very important object of the ina. vention is to produce ceramic material having the above'mentioned characteristics from raw materials which may be obtained in large .quantities and at relatively low cost, whereby the final product may be cheaply and, efliciently manufactured.

Attempts have previously been made to produce lightweight porous blocks particularly designed for their refractory qualities, and intended for use as fire brick, furnace linings or the like.. The materials used in the production of such as ingredients of such blocks, they have accordingly generally been selected for their high alumina and relatively low silica content, this combination being intended to increase the resistance to heat. So far as I am aware, no successful porous structural light-weight brick has been produced prior to my invention, and the success of the present invention is believed to be due tolthe careful selection of ingredients, which,

,, after much experimentation, have been found to produce blocks of light weight and great strength Alkalies (NazO and K2O)-; triace Loss on ignition weight of the total mixture. The sizeof particles sufiicient to support the greatest. loads they may a be called upon to bear. 7

According to my process, the product isproe duced. from a clay selected for its desirablequali ties for this particular purpose, namely the manufacture of light-weight structural brick; The clay is mixed with a lignite, likewise selected for its particular adaptability in the manufacture of the desired product, and with these two ingredients is preferably mixed a suitable quan- 10 tity of bentonite.

The clay selected should be of good plasticity, and should have good working properties. :It should have a sufficient vitrification range'so that it can be vitrified without sagging or warping. A clay having excessive shrinkage should be avoided. The clays which have been most successfully used have been silicious clays that are quite free from impurities, andwhich have a vitrification range between cones 8 and 20, or. between approximately 2237 F. and 2768 F. An average analysis of such clays is given as follows:

Range 5o-1'70% la-% 0.5-1.5%

o.2 o.5%& 03-05% trace 7.0% 5-9% The clays have good plasticity, the shrinkageon drying and firing is low, they have good mechanical strength and the vitrification range is suffi cient so they can be burned to low porosity without losing their shape or warping. The fusion temperature of these clays ranges from 2800 F. to 2900 F. p

The second important ingredient is lignite, The lignite employed should be hard and strong, so that it may be crushed to a definite particle size. It should be of a character such that it will not disintegrate during the mixing and wetting of the mixture. The fusing temperature of the ligniteash should be between 200091 and 2100 F., so that it will act as a fiux on the claywith out requiring too high a temperature in firing the Ware. 7 The size and quantity of the lignite particles may be controlled in the mixture to give the type of ware desired. The lignite shouldbe carefully graded according to size. The quantity, 0 of lignite used may vary from 40% to .by

Silica (SiOz) 67.0% Alumina (A1203); 23.0% Iron oxide (F6203) 1.0% Lime (CaO) r 0.3% Magnesia (MaO); 0.5%

may vary from 0.5 inches to 0.02 inches. The fol-:-

ENT *oFFicefT The lignite used is selected for the low fusion temperature of its ash as well as for its hardness. Such lignite is available in large quantities in the State of North Dakota, and in its natural state contains a large percentage of alkalies, which, when the lignite is burned, results in anjash having a high alkaline content which is desirable in the production of the final ceramic product.

It is brokenby crushing into particles ranging in size from one-half inch to two-hundredths inch and screened. The fragments are asa rule'about twice as long in one dimension as in the other two. As a result, they interlockand touch when the product is formed. When the lignite is burned out during the firing of the ware, the openings left where the lignite particles were are found to be connected at the ends and walled on the sides with a vitreous coating formed by the fusion of the lignite ash and the other ingredients" Since about fifty per of the body of the ware. cent by weight of the mixture is made up of lignite, which has a specific gravity of about 1.2, whil'ethe clay substance has a specific gravity of about 1.9, the mixture by volume, therefore,

contains more than fifty per cent of lignite, and when the lignite has been burned out there are many of the connected openings lying between thin walls of vitreous material.

Bentonite is used in smaller quantities in combination with the two above mentioned principal ingredients up to 10% by weight of the clay. Bentonite is a mineral of a colloidal nature and clay-likeproperties, but has a much greater plasticity and much higher shrinkage. It is made up of minerals not found in clay to any great ex-' tent. The analysis approaches that of a clay, and; there isithesame variation in composition in bentonites as in clays. Its fusion-temperature ranges from" about'2100- F. to 2300 F. It is used only insmall quantities because of its'highshrinkage on drying. In amounts up to 10% of the weight of the clay used, it adds greatly tothe plasticity. of the mixture, increases the mechanical strength of the dry ware and also of the fired ware- It acts as a flux with the clay and lowers the temperature required for vitrifying the body of the ware. Its use permits the use of larger quantities of the crushed lignite and the obtaining of a body of ware of greater porosity.

The process of manufacture varies somewhat with the particular product to be obtained, but broadly speaking is as follows:

The clay is pulverized and to it is added pulverized bentonite. The lignite is crushed and screened and the size of the particles is definitely controlled in this manner. The'proper quantities of lignite, clay and bentonite are thoroughly mixed in a dry condition and are then made plasticby the'addition of water, and the ingredients thoroughly pugged or mixed. The ware isthen formed by any plastic process. Most of the desired products may be made on an auger machine, where the clay is forced out through a die in the desired shape and cut off to the proper length. The ware may then be dried in a common manner, but the drying requires less time than usual, due to the large quantity of the lignite present. After being dried, the product is .placed in a kiln and fired. Sufficient air for oxidation of the combustible material in the ware must be supplied and suflicient time allowed to permit oxidation to take place before the temperature is raised to that required for vitrification of the ware.

The structural ceramic material produced thereby is light in weight and yet sufficiently strong to carry the loads to which it may be subjected. The body of the material is full of cells whichpare interconnected and whose size and number may be controlled by suitably regulating the size and quantity of the lignite employed. By removing the surface skin and exposing the outer cells,a material is produced which acts as an absorber of sound. The absorbing of sound of varying pitches may be controlled by varying the, size and number of cells. By vitrifying the ware, thus providing a veneer or surface skin, a ware may be produced which is capable of resisting absorption of water and which is also resistant to the ordinary abrasion to which such materials are subjected in use.

The ware may be made into structural units of various sorts and has the advantage of having very low weight, great strength and resistance to weather. It may be used as a wall surfacing on the interior of buildings to absorb sounds and to reduce reverberation. It may be used in various forms and in Various ways for the absorption of sound under various conditions. It may be used in the form of a hollow cylinder to absorb the sound from the exhaust of internal combustion engines.

face. It may be employed also in the manufacture of hollow tile, solid tile, partition the and partition block's. i

This type of ceramic structural material fulfills a long-felt need, in that it reduces the load on building or other structures, and consequently reduces the cost of construction by requiring less massive foundations and frames for carrying loads. The material is fire-proof, strong, durable, and resists the natural destructive forces to which such materials are ordinarily exposed, such as water, snow, sleet, wind, dust, gases, etc.

The excellent sound absorbing qualities of the ware are apparently due to the numerous connected pores or openings present in the ware. This has been proved by actual tests. So far as I am aware, no similar fired structural ceramic material has been developed prior to the present invention. No sound absorbing material is at present available having the qualities of the present product, namely fire-proofness, resistance. to abrasion, water-proofness and a natural surface finish combinedwith'high sound absorbing properties.

While it is true that other materials havebeen proposed employing carbonaceous material as an initial ingredient for the purpose of forming pores in the finished material, nevertheless such carbonaceous materials have been used in more finely divided form and, in smaller amounts than in the present invention, so that the resulting product, although lighter in weight than a solid unit of the same size, was filled with pores or cells of small size which were not connected. The weight of previous units might be from 15% to 30% It may be used in making building brick with or without a vitrified veneer on theless than the corresponding size of ordinary brick. The porosity and lightness of .previous materials could not be increased substantially beyond the 30% limit without so weakening the brick that it became no longer available for structuralpurposes. 1 According to the present invention, the weight of the unit may be reduced from 35% to as compared with the weight of an ordinary brick, while-at the same time possessing great strength, making it available for any structural uses. This is due to the fusing effect which takes place between highly alkaline lignite and the clay containing a high silica content, combined with theuse of a smaller quantity of bentonite up to 10% by weight of the clay. In the ipresent'prod uct the pores or openings are connectedand offer no obstruction to the passage of air and sound. By placing a block to the mouth and blowing on it, the air escapes in all directions.

The following products may be mentioned as illustrative of the type of article which may be manufactured from material made in accordance with my invention:

Common brick.These.may be made in larger sizes than the standard brick because of their lower weight. Accordingly the laying of brick using the product produced according to the pres- .ent invention is greatly facilitated. Moreover, the brick, due to the large pores in theface of the material, bond well withthemortar; Plaster or stucco will adhere to this type of brick much more readily than to ordinary brick because of the pores or openings. 1 1

Face brio7c.These may also be made in larger size than standard brick. The face may be veneered with a vitreous coating to exclude moisture. Face brick manufactured in accordance with my inventionpossesses the advantages of lower weight, greater strength and better insulation than ordinary materials employed.

Hollow tile-Hollow tile produced from materials manufactured in accordance with the present invention are light in weight and can be sawed and will holdnailsk The nails can be driven into the tile withoutsplitting, and the The materialwill grip the nails as Wood does. tile will hold stucco or plaster Well and may be veneered and finished on the exposed surface so that no other finish or surfaceis necessary.

'Partition,tile. such tiles produced in accordance with my invention may be made in larger sizes than ordinary because of theirlow'specific gravity. The tiles may be made so that they require no other surface finish andthus serve to cheapen construction. Such tiles are found to absorb noises and sounds. The tile may easily be dressed to plane surfaces and exact dimensions. Moreover. the mortar joints may be very thin. The material is fire-proof, water-proof and a good insulator for heat "and sound.

Wall tile-These may be made with a vitreous veneer finish. Wall tiles prepared in accordance with my invention have the advantage of low weight and the mortar or cement adheres to-them much better than to ordinary tiles. The .tile

may be used either on interiors or exteriors.

Terra-cotta body.The body of terra-cotta may be made of porous ceramic material produced in accordance with my invention, resulting in reduced weight and insuring: better ad herence to mortar or cement. The surface may be veneered and. treated as desired.

Acoustic tzZe.Such tile may be madewith ;pores -or o peningsof exactly regulated size. Such tiles atsorb' fthefnoises or sounds within buildings, class-rooms, auditoriums, halls, ofiices, hospitals and hotels. 7 The tilemay 'be made with whatever Y thickness or size is necessary. The tile may be, so finished on the exposed surface as to require 11 no further surface treatment. Such tile is fireproofpwater-proof and an absorber of heat and soun'dQ A specific example of the use of such acoustic tile is on the muflier of an internal combustion engine. 1

For the purpose of more fully understanding the invention, a specific example of the production offaparticularproduct is given by way of illustration; The" particular product produced according to this example is an acoustic tile of rectangular cross section having a finished size of 2 inches-x 12 inches-x 12 inches, with smooth and plane surfaces to permit the use of verynarrow joints in laying thetile.

Eimmple.To make this acoustic tile, I take 475 lbs. of clay, 25 lbs. of bentonite and 500 lbs. of lignite, with the lignite particles all finer than 8 mesh and coarser than 28 mesh, and per cent of the particles finer than 12 mesh andcoarser than 20 mesh.- l

The composition of the clay used is as follows:

Silica 66.5%, alumina- 23.3%, iron oxide 11%,

lime 0.3%, magnesia 0.6%, alkalies a trace. The I Silica 21.5%, alumina 11.4%, iron oxide 14.4%,

lime 19.0%, magnesia 7.3%, alkalies 10.1%. The fusion temperature of the ash is 2095 F.

I thoroughly mix the bentonite with the clay in a dry'condition and then the sized lignite is added and thoroughly mixed dry with the other ingredients.

continued'until the mass is plastic and coherent and of the proper temper towork well in an Sufiicient water is then added and the mixing auger press, which is used in forming the Ware. 1

The plastic mixture is fed tothe press and is extruded through the die of the press in a column' of the size desired. The column'is then run on a cutting table and cut to the'desired lengths.

The tile are sufficiently strong and'rigid to be handled and are placed on the'racks of a drier car. When the car is loaded, it is transferred to thedrier and the tilesare completely dried in twenty-four hours. r The dried tiles are then transferred to the kiln.

A rectangular downdraft kiln of the periodic type may be used, but preferably a tunnel kiln may be employed because of itsbetter control. Because of the large amount of combustible matter in the ware it is necessary to stack itjirt the kiln so that all the faces except the bottom are exposed to the atmosphere of the kiln. This makes it necessary to use'racks of refractory material or posts and shelves such as are used kilns for stacking many other ceramic wares.

The temperature of the kiln is raised gradually to the temperature at which'the combustion of the lignite commences (a lowredheat) (about I 1100 F.). The temperature is held at this point and the kiln atmosphere socontrolled that oxidation of the lignite in the Ware willtake place t he r p r. ra ie se a e? f the lignite has been completed, the temperature is, raised more rapidly: to thetemperature required tovitrify the clay body of the: ware-- (about 2200F.). g I I After theware has been vitrified, it is allowed to cool gradually until the kiln. can be opened and thew-are removed. Theware after removal from thekiln-is dressed on a dressingwheel.- to proper dimension and to smooth plane surfaces. At the same time the outer skin is removed so that the pores oropenings are uncovered;

The ware has the following physical. characteristics: 1) It is greyisnwhiteincolor; (2) it isharder than steel; (3) the surface is plane; but pitted with holes varying in size from 0.02 inch to 0.25 inch; (4 theweight of a2" :4 12" x 12" tileaverages about 9.5 lbs; (5) the tiles have a crushing strength of l800-lbs. per squareinch.

When examined under a magniI-yingglass, the

walls or partitions between. the cells. are seen: to

be made up of a vitreous, glossy material formed by the fusion of the; lignite-ash upon the surface of the clay and bentonite mixture. The cells are angular and connected, dueto-the-interlocking of the lignite particles during the formingofthe were When. tested for; sound absorption, the tile absorbed. 58.0 units at 512 cycles.

Approximately 60% of the surface and, 60%

-. of the volume is made-up of cells or openings.

Theimproved ceramic material is characterizedby its lightness combined with great strength.

The strength is apparently due to vitreous or glassy films formed throughout the bodyof the material, due to the reaction between the highly alkaline fusible ash resulting from the burning of the lignite with the high silica clay, preferably. in combination with the bentonite, which acts-as aflux and reduces the temperature at which the ware must be fired tobecome vitrified.

These films form around the cavities formerly occupied by the pieces of lignite; before burning. On account of high strength. a relatively large proportion of lignite may be employed, andrelatively large particles-used, resulting in; high po-- rosity and lightness in the finished. product. Due also-to the high strength. of the material, the porosity may be varied within Widelimits according to the desired. use towhich the finished product is to be put, by suitably regulating the size and quantity of the lignite particles employed. The present product also difiersradical- 1y from any products previously developedinthefactthat the pores are large and interconnected. Another novel characteristic of the present product is the ease with which it may be cut,.and.its

property of receiving drivennails or. the, like, and

gripping the same like wood. A structural ceramic unit containing. .a driven nail which is gripped like wood is. believedto be a novelarticle of manufacture.

WhatIclaim is:v

l. A brick having alight-weight burned. clay body'originally, comprised offcl'ay of high silica and low alumina content", lignite high in alkaline content, and bentonite up. to: by weight, of the:- clay, said body having. large; interconnected cavitiesdistributed throughout, the walls of the cavities being; coveredby a coating of fused: silica and analkali.

2. Porous light-weight. sound-proof structural ceramic material: produced by burning a mixture of; 475-parts byweight of. clay, partsbentonite and; 500' parts lignite, said materialhaving large interconnected pores.

3.; A. baked} ceramic tilederived from clay, lignite: and bentonite,.said;tile-being of greyish white color, hardness greater than steel, its surface pitted with. holesvaryingin: size from .02 inch; to .25 inch, a; weight of 9.5 lbs. fora tile 2." by 12 by 12., having: a crushing strength: of substantially 180.0-1bs. per square inch and having inter connected pores- 4. A process for producing light-weight porous structural material: of great strength and having large interconnected pores; comprising mixing pulverized clay: of high silica and low alumina content with pulverized lignite having high alkalicontent, all the-particles of thezligniteranging from 8-28.mesh and at least 50% of 'theparticles beingofless'than 12. mesh, moistening the mass sufiiciently to render the same plastic, forming. the plasticmass-into blocks, heating the blocks sufiiciently tocause oxidation of the carbonaceous portion of the lignite leaving large interconnected pores, their raising thetempera-- ture. to a point sufficient tofuse the lignite ash and the silica of the clay to provide a; glassy film over-thewallsof the pores and-to vitrify the Ware,

bentonite-being mixed with the clay and lignite toserveas aflux.

5. A processes set. forthin claim l wherein the oxidation of the. lignite commences at 1100 F.

andv the final vitrifying. temperature is approxi-- mately 2200 a 6. A compositionv of matter adapted to be burned for producing. structural material of high.

porosity and. great strength. and having large in.- terconnected. pores, comprising a mixtureof clay of. high. silica co'ntent. and low alumina. content.

and. a lignite. of high alkalinity, the lignite being usedin the. proportionof -70% by weight of. thetotallmixtureits particles. being. all finer than. 8 mesh. and. coarser than.28.meslr ancL'75%v of the particles being. finer than l2.mesh,. said composition including also-bentonite. as a. flux.

7;v A. composition. of matter adapted. to be burned. for they preparation of. porous ceramic structural. material comprising. principally clay. and. lignite, the lignite being used in a proportion of LO-70% by weight of. the total mixture, the. clay being of highplasticity, having. a vitrification. range. between. approximately 2237" F.. and2768. F., afusiontemperatureof 2800" lkto.

2900 F., and. including as constituents, silica. -70%, alumina l8.-25.%,. iron. oxide. .5-l.5%, lime .2.5%, magnesia .3.'T%, anda trace of alkalies, the lignite being ofhighalkaline content, the, particles. of lignite varying between .5' inches and .02. inchesv and an. ash contentwhen burned of approximately 5% of the weight. of; the lignit'e,

perature of cone 22, vitrification point at'cone 14, and a composition comprising the following ingredients in substantially the following proportions by weight: silica. 66.5%; alumina 23.3%, iron oxide 1.1%, lime 3%, magnesia, .6% and alkalies a trace; the lignite constituting about 50% by weight of the total mixture, its particles being all finer than 8 mesh and coarser than 28 mesh, 75% of the particles finer than 12 mesh and coarser than 20 mesh, said lignite containing about 30% moisture, and about 6.6% ash having the following composition: silica 21.5%, alumina 11.4%, iron oxide 14.4%, lime 19%, magnesia 7.3%, alkalies 10.1%, and a fusion temperature of 2095 F., the clay, bentonite and lignite being employed in the proportions of 475 lbs. clay, 25 lbs. bentonite and 500 lbs. of lignite, the bentonite having a fusion point at cone 7 and approximately the following composition: silica 67.8%, alumina 18.2%, iron oxide 6%, lime 1.9%, magnesia .9% and sodium oxide 65%.

9. A composition of matter adapted to be burned for producing structural material of high porosity and great strength and having large interconnected pores, comprising a mixture of clay of high silica content and low alumina content, lignite of high alkalinity, and bentonite up to 10% by weight of the clay.

10. A brick having a baked clay body having large interconnected pores, said body originally comprising clay permeated by particles of lignite high in alkali content, togetherwith bentonite up to 10% by weight of the clay, the alkali content being adapted for fluxing the clay in baking and forming a glassy film upon the surfaces of the cavities previously occupied by the particles of lignite.

CHARLES WEIGEL. 

